Semiconductor device and method of controlling semiconductor device

ABSTRACT

A semiconductor device includes a connector connectable to a host, a power supply circuit which includes an input portion that receives first power from the host via the connector, an output portion, and a switch that is connected to the input portion and the output portion and controls whether to supply the first power to the output portion, the power supply circuit generating second power and third power from the first power, a semiconductor memory which receives the second power from the output portion, and a controller which receives the third power from the output portion and controls the semiconductor memory. The power supply circuit turns off the switch and stops supply of power to the semiconductor memory and the controller when the second power exceeds a first value or when the third power exceeds a second value.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/426,267, filed on Feb. 7, 2017, which is based upon and claims thebenefit of priority from Japanese Patent Application No. 2016-156676,filed on Aug. 9, 2016, the entire contents of which is incorporated byreference.

FIELD

Embodiments disclosed therein relate to a semiconductor device and amethod of controlling a semiconductor device.

BACKGROUND

A semiconductor device in which a power supply circuit including a powersupply IC is supplied with power from a host and supplies power(voltages) to a controller, a NAND memory, and the like is known.

It is preferable that a semiconductor device including a power supplycircuit can improve convenience for a user.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1C are diagrams illustrating an example of an appearance ofa semiconductor device according to a first embodiment, where FIG. 1A isa top view, FIG. 1B is a side view, and FIG. 1C is a bottom view;

FIG. 2 is a diagram illustrating an example of a system configuration ofthe semiconductor device according to the first embodiment;

FIG. 3 is a block diagram illustrating a configuration of a power supplyIC according to the first embodiment;

FIG. 4 is a diagram illustrating an example of a ball arrangement of apackage of the power supply IC according to the first embodiment;

FIG. 5 is a sequence diagram of the first embodiment illustrating powerwhen a reset state of a controller is released; and

FIG. 6 is a block diagram of a second embodiment illustrating aconfiguration of a power supply IC and a periphery thereof.

DETAILED DESCRIPTION

Hereinafter, embodiments will be described with reference to theaccompanying drawings.

In this specification, some elements are referenced by plural expressionexamples. The expression examples are merely exemplary, and do not denythat the elements can be expressed by other expressions. Elements whichare not referenced by plural expressions may be expressed by otherexpressions.

The accompanying drawings are schematic, and relationships ofthicknesses and two-dimensional sizes, ratios of thicknesses of layers,and the like may be different from real ones. Parts having differentdimensional relationships and ratios may be included in the drawings.

First Embodiment

FIGS. 1A to 1C illustrate an example of an appearance of a semiconductordevice 1 according to an embodiment. FIG. 1A is a plan view, FIG. 1B isa bottom view, and FIG. 1C is a side view.

FIG. 2 illustrates an example of a system configuration of thesemiconductor device 1 according to a first embodiment.

The semiconductor device according to this embodiment is a memory systemsuch as a solid state drive (SSD), but is not limited thereto.

As illustrated in FIG. 2, the semiconductor device 1 is connected to ahost 2. In this embodiment, the host 2 may be various electronic devicessuch as a notebook portable computer, a tablet terminal, detachablenotebook PC, and a mobile phone. The host 2 may be a server device whichis used for a data center or the like. The semiconductor device 1 can beused as an external memory of the host 2.

As illustrated in FIGS. 1A to 1C and FIG. 2, the semiconductor device 1includes a substrate 11, a nonvolatile memory 12, a controller 13, avolatile memory 14 that can operate faster than the nonvolatile memory12, an oscillator (OSC) 15, an electrically erasable and programmableROM (EEPROM) 16, a power supply circuit 17, a temperature sensor 18, andother electronic components such as a resistor and a capacitor. In FIGS.1A to 1C, the oscillator 15 and the EEPROM are not illustrated for thepurpose of convenience of explanation.

The nonvolatile memory 12 is, for example, a NAND type flash memory(hereinafter, abbreviated to a NAND memory). In the followingdescription, the nonvolatile memory 12 is referred to as a “NAND memory12,” but the nonvolatile memory is not limited thereto and may be othernonvolatile memories such as a magnetoresistive random access memory(MRAM).

The volatile memory 14 is, for example, a dynamic random access memory(DRAM). In the following description, the volatile memory 14 is referredto as a “DRAM 14,” but the volatile memory 14 is not limited thereto andmay be other volatile memories.

The NAND memory 12 and the controller 13 in this embodiment arerespectively mounted as a semiconductor package which is an electroniccomponent. For example, as the semiconductor package of the NAND memory12, plural semiconductor chips (memory chips) are stacked andencapsulated in a single package.

The substrate 11 is, for example, a substantially rectangular circuitboard formed of a material such as a glass epoxy resin and definesexternal dimensions of the semiconductor device 1. The substrate 11 hasa first surface 11 a and a second surface 11 b which is located oppositeto the first surface 11 a. The first surface 11 a and the second surface11 b may be referred to as, for example, principal surfaces. In thisspecification, surfaces other than the first surface 11 a and the secondsurface 11 b among surfaces of the substrate 11 are defined as “sidesurfaces.” In the semiconductor device 1, the first surface 11 a is acomponent-mounting surface on which the NAND memory 12 (12 a and 12 b),the controller 13, the DRAM 14, the oscillator 15, the EEPROM 16, thepower supply circuit 17, the temperature sensor 18, and other electroniccomponents such as resistors and capacitors are mounted. The secondsurface 11 b is a non-mounting surface on which the components such asthe NAND memory 12 are not mounted. Since no component is mounted on thesecond surface, a decrease in thickness of the semiconductor device 1and space saving can be achieved, thus a decrease in size and thicknessof the host 2 in which the semiconductor device 1 is mounted can beachieved.

In the semiconductor device 1, components such as the NAND memory 12 maybe mounted on the second surface 11 b. Other functions such as test padsfor checking performance of a product may be provided on the secondsurface 11 b.

As illustrated in FIGS. 1A to 1C, the substrate 11 includes a first edgeportion 11 c and a second edge portion 11 d which is located opposite tothe first edge portion 11 c. The first edge portion 11 c includes aconnector 21 (an interface portion, a substrate interface portion, aterminal portion, or a connection portion). The connector 21 includes,for example, plural connection terminals 21 a (metal terminals). Theconnector 21 is electrically connected to the host 2 and exchangessignals (control signals and data signals) with the host 2.

The semiconductor device 1 is electrically connected to the host 2 viaan interface 3. The host 2 performs data access control on thesemiconductor device 1 and performs writing, reading, and erasing ofdata with respect to the semiconductor device 1, for example, bytransmitting a writing request, a reading request, and an erasingrequest to the semiconductor device 1.

The semiconductor device 1 is electrically connected to a host powersupply circuit 4 (a power supply circuit) via a power supply line 5. Thehost power supply circuit 4 provides various types of power, which areused for the semiconductor device 1, via the power supply line 5 and theconnector 21.

An interface 2 according to this embodiment is, for example, peripheralcomponent interconnect express (PCIe (PCI-E)). That is, a high-speedsignal (a high-speed differential signal) based on the PCIe standard istransmitted between the connector 21 and the host 2.

The interface 2 may employ other standards such as serial attached SCSI(SAS), serial advanced technology attachment (SATA), nonvolatile memoryexpress (NVMe), and universal serial bus (USB).

In the connector 21, a slit 21 b is formed at a position departing fromthe central position in the short-side direction of the substrate 11 andis fitted to a protrusion or the like disposed in the connector side ofthe host 2. Accordingly, the semiconductor device 1 can be preventedfrom being reversely attached.

The power supply circuit 17 in the semiconductor device 1 iselectrically connected to the host power supply circuit 4 via theconnector 21 and the power supply line 5. The power supply circuit 17 issupplied with power required for the semiconductor device 1 from thehost power supply circuit 5. The power supply circuit 17 supplies powerto the NAND memory 12, the controller 13, and the DRAM 14. It ispreferable that the power supply circuit 17 be disposed in the vicinityof the connector 21 to suppress a loss of power supplied from the host2.

The power supply circuit 17 includes a power supply IC 17 a (FIG. 1A),and electronic components such as resistors, capacitors, and inductorsare connected to the power supply IC 17 a. The power supply IC 17 a willbe described later. The power supply IC 17 a may be referred to as apower supply circuit, a power supply chip, or a complex power supplycontrol IC and the power supply IC 17 a is, for example, a powermanagement integrated circuit (PMIC).

The power supply IC 17 a according to this embodiment is, for example, awafer level chip size package (WLCSP) and at least one chip is packaged(encapsulated). The power supply IC 17 a is not limited thereto.

The controller 13 controls the operation of the NAND memory 12. That is,the controller 13 controls writing, reading, and erasing of data in theNAND memory 12. The controller 13 controls a garbage collection processor a wear levelling process in the NAND memory 12.

The garbage collection process is a process of transferring data otherthan unnecessary data in a physical block to another physical block andreleasing the original physical block to efficiently use an area in thephysical block of the NAND memory 12 to which unnecessary (invalid) datahad been written. In other words, the garbage collection process is aprocess of writing (copying) valid data in a physical block to anotherphysical block and erasing all data in the original physical block.

The wear levelling process is a process of uniformly distributing thenumber of rewriting times to blocks. For example, the wear levellingprocess is a process of transferring data of a block having a largenumber of rewriting times to another block having a small number ofrewriting times. By transferring data which is often rewritten to ablock having a small number of rewriting times and transferring datawhich is less rewritten, such as an OS file of a computer, to a blockhaving a large number of rewriting times, the number of rewriting timesmay be equalized in blocks. The details of the wear levelling processare not limited thereto.

In this embodiment, the garbage collection process or the wear levellingprocess is performed with a predetermined cycle, but it is not limitedthereto and the process may be performed in accordance with a commandfrom the host 2 or the process may be performed at each time whenwriting, reading or erasing of data in the NAND memory 12 correspondingto the command from the host 2 is finishied.

The controller 13 includes a reset input, performs initialization(reset) of the state of the controller 13 or release of a reset state inresponse to an input signal, and starts normally (safely) thesemiconductor device 1 as a system. The signal which is used to releasethe reset state is referred to as, for example, POWER ON RESET. In thefollowing description, “switch to a reset state” includes a case inwhich an original reset state is maintained.

The DRAM 14 is an example of a volatile memory as described above and isused to store management information of the NAND memory 12, or to cachedata and the like. The oscillator 15 supplies an operation signal of apredetermined frequency to the controller 13. The EEPROM 16 stores acontrol program and the like as fixed information.

The temperature sensor 18 monitors, for example, the temperature of thecontroller 13. The temperature sensor 18 is disposed, for example, inthe vicinity of the controller 13 on the substrate 11, but the positionof the temperature sensor 18 is not limited thereto. The temperaturesensor 18 does not need to be disposed on the substrate 11 and may bedisposed as one function of the controller 13.

The temperature sensor 18 measures the temperature around the positionat which the temperature sensor 18 is disposed, but the temperaturemeasured by the temperature sensor 18 may be referred to as the“temperature of the semiconductor device 1.” When the temperature sensor18 is disposed in the vicinity of the controller 13, the temperaturemeasured by the temperature sensor 18 may be referred to as the“temperature of the controller 13.”

When all components mounted on the substrate 11 are disposed on only thefirst surface 11 a as described above, the second surface 11 b is acomponent-non-mounting surface on which no component is mounted. In thiscase, in comparison with a case in which a mounted component protrudingfrom the surface are mounted on both surfaces of the substrate 11, it ispossible to achieve a decrease in thickness of the semiconductor device1 and to achieve a decrease in size and thickness of the host 2 on whichthe semiconductor device 1 is mounted.

FIG. 3 is a block diagram illustrating a configuration of the powersupply IC 17 a according to this embodiment. FIG. 4 is a diagramillustrating an example of a ball arrangement (a solder ballarrangement) of the package of the power supply IC 17 a according tothis embodiment. The power supply IC 17 a according to this embodimentincludes a load switch 170 (switch), a power supply controller 171, andplural power supply channels CH1 to CH4. Each power supply channel maybe merely referred to as a power supply. The number of power supplychannels is not limited thereto.

An input (an input portion) Vin0 of the load switch 170 is connected tothe host 2 (specifically, the host power supply unit 4) via a wire (suchas a wiring layer or an internal wire) disposed in the substrate 11, theconnector 21, and the power supply line 5. The input Vin0 of the loadswitch 170 is supplied with power (first power) from the host powersupply circuit 4.

An output (output portion) Vout0 of the load switch 170 is electricallyconnected to inputs Vin1 to Vin4 of the power supply channels CH via theoutside of the power supply IC 17 a. In other words, power is suppliedfrom the output Vout0 of the load switch 170 to the power supplychannels CH of the power supply IC 17 a via a wire (a wiring layer, aninternal wire) disposed in the substrate 11.

On the other hand, when the load switch 170 is switched to an OFF state,the supply of power to the power supply channels CH is stopped (orintercepted or interrupted).

In this embodiment, the power supply channel CH1 is, for example, a lowdrop out (LDO). The power supply channels CH2 to CH4 are, for example,DC/DC converters. The power supply channels CH1 to CH4 include registersR1 to R4, respectively.

The LDO is a linear regulator and is a circuit system that convertsinput power into desired output power by forcibly consuming the inputpower using ON-resistance of a power device (a pass transistor) such asa power metal oxide semiconductor field effect transistor (power MOSFET)or a power transistor. The LDO means that it operates as a regulatoreven when a potential difference between the input and the outputthereof is small.

The DC/DC converter is a switching regulator, and serves as a DC powersupply which switches an input voltage, outputs a switching pulse, andsmooth the output pulse using a filter including an inductor and a coil.

In this embodiment, the output Vout2 of the power supply channel CH2 isconnected to the controller 13 and supplies a predetermined voltage(third power) to the controller 13. The output Vout3 of the power supplychannel CH3 is connected to the DRAM 14 and supplies a predeterminedvoltage to the DRAM 14. The output Vout4 of the power supply channel CH4is connected to the NAND memory 12 and supplies a predetermined voltage(second power) to the NAND memory 12. The types or connections of thepower supply channels CH are not limited to the above description, butcan be appropriately changed.

The power supply channels CH1 to CH4 have an overvoltage protectionfunction. The overvoltage protection function may be referred to as anOVP function. Hereinafter, the overvoltage protection function will bedescribed as OVP function.

In this embodiment, the OVP function works (starts) when the outputvoltage of each power supply channel CH is greater than a predeterminedvalue (a threshold value). More specifically, for example, when theoutput voltage Vout of the power supply channel CH1 is greater than apredetermined value Vth, the OVP function of the power supply channelCH1 works. The OVP function works, for example, when the input and theoutput of each power supply channel CH are short-circuited and anovervoltage is input to the output side.

The register R of each power supply channel CH stores a monitoringresult concerning whether or not the above-mentioned OVP function ineach power supply channel CH works. In this embodiment, in a state inwhich the OVP function does not work (an initial state), “1” is held(record, set) in each register R. On the other hand, “0” is held(record, set) in the register R of each power supply channel CH in whichthe OVP function works. The registers R may be referred to as, forexample, “POWER GOOD (PG) register.” Each register R may be configuredto always monitor the corresponding power supply channel CH or may beconfigured to monitor the corresponding power supply channel CHperiodically (for example, for each cycle T1).

“0” may be held (record, set) in each register R in a state in which theOVP function does not work, and “1” may be held (record, set) in theregister R of the power supply channel CH of which the OVP functionworks. Information stored in the registers is not limited to the abovedescription, but at least information indicating whether the OVPfunction of the corresponding power supply channel CH works is stored.

The power supply controller 171 controls ON/OFF of the load switch 170.The power supply controller 171 monitors the registers R of the powersupply channels CH1 to CH4. The power supply controller 171 switches theload switch 170 to OFF when any value of the registers R1 to R4 to bemonitored is changed from “1” to “0,” that is, when the OVP function ofany power supply channel CH works. The power supply controller 171 stopsthe supply of power to each power supply channel (each power supply) byturning off the load switch 170. When the OVP function of any powersupply channel CH works, the power supply controller 171 may reset thecontroller 13.

The power supply controller 171 may always monitor the registers R ormay monitor the register R periodically (for example, for each cycleT2).

On the other hand, the power supply IC 17 a includes a POWER ON RESEToutput. The POWER ON RESET output according to this embodiment ischanged from LOW to HIGH when the power supply IC 17 a is supplied withpower from the host power supply unit 4 and the output voltages of allthe power supply channels CH1 to CH4 are stabilized. A sequence diagramat this time is illustrated in FIG. 5. The controller 13 releases itsreset state in response to the POWER ON RESET output and starts normally(safely) the system of the semiconductor device 1. The sequenceillustrated in FIG. 5 can be realized, for example, by a logic circuitbut the embodiment is not limited thereto.

In the semiconductor device 1 according to this embodiment having theabove-mentioned configuration, when the output voltages of all the powersupply channels CH1 to CH4 are stabilized, the POWER ON RESET output isswitched from LOW to HIGH and the reset state of the controller 13 isreleased.

For the purpose of comparison, a case in which a reset IC or a CR resetcircuit which is externally attached (outside the power supply IC 17 a)is used to release the reset state of the controller 13 is considered.The power supply channels CH output the voltages when power is suppliedto the power supply IC 17 a from the host power supply unit 4, but thetimes required for stabilizing the output voltages thereof may bedifferent from each other. Accordingly, when the reset IC or the CRreset circuit independent of the power supply IC 17 a is used, the timeafter power is supplied to the semiconductor device 1 from the hostpower supply circuit 4 until a signal for releasing the reset state ofthe controller 13 is output needs to be set to be long.

Therefore, in this embodiment, the POWER ON RESET output is switchedfrom LOW to HIGH to release the reset state of the controller 13 by thefunction of the power supply IC 17 a as described above. Accordingly, itis possible to release the reset state of the controller 13 rapidlyafter the output voltages of all the power supply channels CH1 to CH4are stabilized, thereby contributing to shortening of a system startingtime.

The operation of the semiconductor device 1 according to this embodimentwhen the OVP function of the power supply channel CH2 works will bedescribed below. When the output Vout2 of the power supply channel CH2is greater than the predetermined value Vth, the OVP function of thepower supply channel CH2 works. The register R2 sets (changes) its valuefrom “1” to “0” in response to the working of the OVP function of thepower supply channel CH2.

Then, the power supply controller 171 monitoring the register R2 checksthat the value of the register R2 is “0” and switches the load switch170 from ON to OFF. In this way, it is possible to stop the supply ofpower to each power supply channel CH when the output Vout2 of the powersupply channel CH2 is an overvoltage.

For example, when a protection circuit designed to open its output sideif the OVP function works is used, the input voltage is outputcontinuously without any change, thus a component located in a powersupply destination has a possibility to be affected. When a protectioncircuit designed to be short-circuited to the ground (GND) using aswitching element such as a MOSFET if the OVP function works, is used,an overcurrent may continue to flow in the switching element to destroythe power supply IC 17 a.

As illustrated in FIG. 4, in the power supply IC 17 a, an input pin(terminal, electrode, or ball) Vin and an output pin (terminal,electrode, or ball) Vout of load switch 170 and each power supplychannel CH, and an output feedback pin (terminal, electrode, or balls)FB are arranged to be close to each other. The ball pitch is small (forexample, 0.4 mm) for the purpose of an increase in the number of powersupply channels and a decrease in the size of the power supply IC 17 a.Accordingly, when a stress is externally applied or when conductivesubstance is interposed between the balls, the input pin and the outputpin may short-circuit. FIG. 4 illustrates a part of the pin arrangement.The feedback pin FB may be internally connected to the input pin Vin ofthe corresponding power supply channel CH and used as an auxiliary inputpin of an external output Vout0 of the load switch 170, or may be usedas a signal output pin from the power supply controller 171 to thecontroller 13.

Therefore, in the power supply IC 17 a according to this embodiment,when the input and the output of any power supply channel CH areshort-circuited or the like and an overvoltage is input to the outputside, the load switch 170 is turned off by the power supply controller171. Accordingly, each power supply channel CH is not supplied withpower.

Accordingly, it is possible to prevent an overvoltage from being appliedto the components (such as the NAND memory 12, the controller 13, andthe DRAM 14) connected to the output side of the power supply channelsCH. Even when it is short-circuited to the ground, it is also possibleto prevent an overcurrent from continuously flowing in the switchingelement to destroy the power supply IC 17 a.

Second Embodiment

A second embodiment will be described below. The same elements as in thefirst embodiment will be referenced by the same reference numerals anddetailed description thereof will not be repeated. FIG. 6 is a blockdiagram illustrating a configuration of a power supply IC 17 b accordingto this embodiment and a periphery thereof. In this embodiment, a loadswitch 175 is disposed independent of the power supply IC 17 b (outsidethe package of the power supply IC 17 b, that is, independent of thepower supply IC 17 b) and the output Vout0 of the load switch 175 isconnected to the inputs of the power supply channels CH of the powersupply IC 17 b. The power supply IC 176 and the load switch 175constitutes a power supply circuit.

In this embodiment, the power supply IC 17 b includes a POWER GOODoutput. The POWER GOOD output is a signal indicating whether aprotection function works in the power supply IC, distinguishes whetherthe protection function works or not, for example, by “LOW” and “HIGH”or “LOW” and “Hi-Z,” and outputs the value.

The POWER GOOD output of the power supply IC 17 b is, for example, anopen drain output. More specifically, an output circuit in the powersupply IC 17 b is provided with a field effect transistor (FET), and thedrain thereof is drawn out to the outside of the power supply IC 17 bwithout being connected inside the power supply IC 17 b.

The POWER GOOD output is pulled up to the input Vin0 side of the loadswitch 175. More specifically, the POWER GOOD output is connected to theinput side of the load switch 175 via a pull-up resistor.

The load switch 175 includes an enable (EN) terminal. For example, theload switch 175 is turned on when HIGH (H) is input to the EN terminaland is turned off when LOW (L) is input to the EN terminal.

On the other hand, as illustrated in FIG. 6, the power supply IC 17 baccording to this embodiment includes a POWER ON RESET output. The POWERON RESET output is designed such that the POWER ON RESET output ischanged to LOW to reset the controller 13 (or not to release the resetstate of the controller 13), for example, when voltage abnormalityoccurs in the output of any power supply channel CH of the power supplychannels CH1 to CH4 of the power supply IC 17 b.

Here, the voltage abnormality refers to, for example, a case in whichthere is a difference of ±10% or more from a desired voltage value ineach power supply channel CH, but this embodiment is not limitedthereto. The allowable range of the desired voltage value may be set to±20% or may be set, for example, to range from −20% to +10%.

In this embodiment, when the OVP function of any of the power supplychannels CH1 to CH4 works, the POWER GOOD signal is output as LOW.Accordingly, the load switch 175 is turned off when the input and theoutput of any power supply channel CH is short-circuited and anovervoltage is input to the output side.

Accordingly, the power supply IC 17 b is not supplied with power and itis thus possible to prevent an overcurrent from flowing in a powersupply destination of each power supply channel CH. In a design which isshort-circuited to the ground when the OVP function works, it is alsopossible to prevent an overcurrent from continuously flowing in theswitching element to damage the power supply IC 17 b.

The system of the semiconductor device 1 can be protected by resettingthe controller 13 (or maintaining the reset state) when voltageabnormality occurs in any of the power supply channels CH1 to CH4. Thepower supply IC 17 b may be designed to turn off the load switch 175 andto cut the outputs of all the power supply channels CH1 to CH4 when thenumber of times in which the output exceeds from the allowable range ofa desired voltage value in any power supply channel CH become greaterthan a predetermined number of times, or when a period of voltageabnormality continues more than a predetermined time.

While some embodiments have been described, the embodiments include thefollowing aspects.

The power supply circuit transmits a signal to the controller forresetting the controller when the second power exceeds a first value orless than a third value smaller than the first value or when the thirdpower exceeds a second value or less than a fourth value smaller thanthe second value.

The power supply circuit turns off the switch when a state in which thesecond power is equal to or greater than the third value and equal to orless than the first value is not maintained for a first period of timeor more or when the state in which the third power is equal to orgreater than the fourth value and equal to or less than the second valueis not maintained for the first period of time or more.

The power supply circuit turns off the switch and/or stops the supply ofpower to the semiconductor memory and the controller when the secondpower exceeds the first value or the third power exceeds the secondvalue.

The power supply circuit transmits a signal to the controller forresetting the controller and/or turns off the switch when the secondpower or the third power is outside a predetermined range.

While some embodiments of the invention have been described above, theembodiments are provided as only examples and are not intended to limitthe scope of the invention. The embodiments may be modified in variousforms and may be subjected to various omissions, substitutions, ormodifications without departing from the gist of the invention. Theembodiments or the modified examples are included in the scope or gistof the invention and are also included in equivalents to the inventionsdescribed in the appended claims. Various inventions can be made byappropriately combining two or more elements disclosed in theembodiments. For example, some elements may be deleted from all theelements described in the embodiments. The elements in other embodimentsmay be appropriately combined.

What is claimed is:
 1. A semiconductor device comprising: a connectorwhich is connectable to a host; a power supply circuit which includes aninput portion that is supplied with first power from the host via theconnector, an output portion, and a switch that is provided between theinput portion and the output portion and that switches to supply thefirst power to the output portion, and which generates second power andthird power from the first power and supplies the second power and thethird power to the output portion; a semiconductor memory which issupplied with the second power from the output portion; and a controllerwhich is supplied with the third power from the output portion andcontrols the semiconductor memory, wherein the power supply circuitfurther includes a first register which indicates whether or not thesecond power exceeds a first value and a second register which indicateswhether or not the third power exceeds a second value, and the powersupply circuit is configured to turn off the switch according to thefirst register or second register to stop the supplying of the firstpower to the output portion.
 2. The semiconductor device according toclaim 1, wherein the power supply circuit further includes a first powersupply channel which outputs the second power, a second power supplychannel which outputs the third power, and a power supply controllerwhich controls the first power supply channel, the second power supplychannel, and the switch.
 3. The semiconductor device according to claim2, wherein the first register notifies the power supply controller thatthe second power exceeds the first value when the second power exceedsthe first value and the second register notifies the power supplycontroller that the third power exceeds the second value when the thirdpower exceeds the second value.
 4. The semiconductor device according toclaim 3, wherein the power supply controller continuously monitors thefirst register and the second register.
 5. The semiconductor deviceaccording to claim 3, wherein the power supply controller monitors thefirst register and the second register on a predetermined cycle.
 6. Thesemiconductor device according to claim 1, wherein the power supplycircuit transmits a signal to the controller for resetting thecontroller when the second power exceeds the first value or is less thana third value that is less than the first value or when the third powerexceeds the second value or is less than a fourth value that is lessthan the second value.
 7. The semiconductor device according to claim 6,wherein the power supply circuit transmits a signal to the controllerfor releasing a reset state of the controller when the second powerexceeds the third value and the third power exceeds the fourth valueafter the controller has been supplied with the first power from thehost.
 8. The semiconductor device according to claim 6, wherein thepower supply circuit turns off the switch if a state in which the secondpower is equal to or greater than the third value and equal to or lessthan the first value is not maintained for at least a first period oftime or if a state in which the third power is equal to or greater thanthe fourth value and equal to or less than the second value is notmaintained for at least the first period of time.
 9. The semiconductordevice according to claim 1, wherein the power supply circuit isdisposed between the connector and the semiconductor memory.
 10. Asemiconductor device comprising: a connector which is connectable to ahost; a switch which includes an input portion that is supplied withfirst power from the host via the connector and an output portion, andthat switches to supply the first power to the output portion; a powersupply circuit which receives the first power from the output portion orthe switch and generates second power and third power from the receivedfirst power; a semiconductor memory which is supplied with the generatedsecond power from the power supply circuit; and a controller which issupplied with the generated third power from the power supply circuitand controls the semiconductor memory, wherein the power supply circuitfurther includes a first register which indicates whether or not thesecond power exceeds a first value and a second register which indicateswhether or not the third power exceeds a second value, and the powersupply circuit further controls the switch according to indications ofthe first and second registers.
 11. The semiconductor device accordingto claim 10, wherein the power supply circuit further includes a firstpower supply channel which outputs the second power, a second powersupply channel which outputs the third power, and a power supplycontroller which controls the first power supply channel, the secondpower supply channel, and the switch.
 12. The semiconductor deviceaccording to claim 11, wherein the first register notifies the powersupply controller that the second power exceeds the first value when thesecond power exceeds the first value and the second register notifiesthe power supply controller that the third power exceeds the secondvalue when the third power exceeds the second value.
 13. Thesemiconductor device according to claim 12, wherein the power supplycontroller unit continuously monitors the first register and the secondregister.
 14. The semiconductor device according to claim 12, whereinthe power supply controller monitors the first register and the secondregister on a predetermined cycle.
 15. The semiconductor deviceaccording to claim 10, wherein the power supply circuit transmits asignal to the controller for resetting the controller when the secondpower exceeds the first value or is less than a third value that is lessthan the first value or when the third power exceeds the second value oris less than a fourth value that is less than the second value.
 16. Thesemiconductor device according to claim 15, wherein the power supplycircuit transmits a signal to the controller for releasing a reset stateof the controller when the second power exceeds the third value and thethird power exceeds the fourth value after the controller has beensupplied with the first power from the host.
 17. The semiconductordevice according to claim 15, wherein the power supply circuit turns offthe switch if a state in which the second power is equal to or greaterthan the third value and equal to or less than the first value is notmaintained for at least a first period of time or if a state in whichthe third power is equal to or greater than the fourth value and equalto or less than the second value is not maintained for at least thefirst period of time.
 18. The semiconductor device according to claim10, wherein the power supply circuit is disposed between the connectorand the semiconductor memory.